The present invention relates in general to client/server data communication systems and more particularly, the present invention is directed towards a method and apparatus that restrains a connection request stream associated with a high volume burst client in a distributed network.
Computer systems are well known in the art and have become a business staple and are also found in many homes. One feature available to the business world is that of using electronic mailing (e-mail) to send and receive messages and other information to and from one another in a business setting. Similarly, home computers, such as desk tops or laptops, and other information devices, such as personal digital assistants (PDAs), allow telecommuting such that a user can connect to the user""s work server and down load and upload messages.
The e-mail system allows clients of a network system, which is maintained by a server system, to send messages or data from one user to another. In order to minimize disk space and requirements as well as to maximize functionality and consistency of the electronic mailing engine used in the network system, the engine is typically located on the server and is merely accessed by a client in order to send messages or retrieve messages to or from another user or client on the server system. In this way, the client system typically allows the user to perform such operations as composing, updating, and sending messages while the server in such a system provides, in part, a server based message repository as well as providing message transmission and reception functions for the user at the client level.
One such email system is described with reference to FIG. 1 showing a messaging system 100 suitable for large, distributed networks such as the Internet or large scale intranet systems. The system 100 typically includes a central server 102 resident in a computer system 104 that can take the form of a mainframe system as well as a distributed type computing system. When the system. 100 is a messaging system, such as an email system, the central server 102, as the central email server, is coupled to an interface, such as a firewall 106, that mediates the flow of information between the mail server 102 and its it clients represented as client 108 , client 110, and client 112. Typically, when the client 108, for example, desires to establish a channel to the server 102, the client 108 will generate a request to open a connection to the mail server 102 by any one of a variety of transports and protocols that are submitted directly by the requesting client 108, via, for example, TCP/IP as an SMTP message from an Internet system. Such a connection request can be submitted by using a dial-up modem using the PhoneNet protocol, DECnet as a MAIL-11 message, DECnet as an SMTP message, UUCP, an X.400 transport, SNA, and so on. For instance, at sites with an Internet connection, Internet addresses are normally routed through an SMTP over TCP/IP channel, however, at sites with only a UUCP connection, Internet addresses would instead be routed through a UUCP channel.
Once the connection request has been accepted, a channel is open between the requesting client 108 and the server computer 102 allowing for the transfer of data. In some cases, however, the requesting client 108 can inadvertantly disrupt the operations of the server 102 by generating a large number of connection requests within a relatively short length of time (i.e., connection request stream) referred to as a connection request burst. A connection request burst is defined as those situations where a legitimate client (referred to as a burst client) as part of its normal operations occasionally generates a short term, high volume connection request stream. One of the problems with the short term connection request burst is that it has the potential to disrupt the server 102 by forcing it to direct an inordinate amount of connection resources to the burst client 108 thereby having the effect of overwhelming requests from other clients, such as client 110 and 112.
A conventional approach to dealing with the short term, burst client 108 is to first identify those clients as burst clients by comparing the client""s current connection request rate a pre-determined threshold. Once identified as a burst client, the burst client is temporarily blocked from making any additional connection requests of the server so as to allow other clients to have access to the server 102.
Unfortunately, however, blocking the connection request stream of the burst client 108, even for a short period of time, can have substantial adverse effects on the burst client 108.
Therefore, it would be desirable to have an improved method and apparatus in a distributed network for providing a burst client access to a server computer without adversely affecting other clients coupled to the server.
To achieve the foregoing, and in accordance with the purpose of the present invention, method, apparatus, and computer readable medium for providing connection requests to a high volume burst client in a distributed network are disclosed. In one embodiment, in a client/server computer environment, a method for restraining a connection request stream associated with a high volume connection request burst client is disclosed. A connection request is received at a beginning of a throttling interval m+1, where the throttling interval m+1 is subsequent to a throttling interval m. A throttling interval m+1 wait time is calculated based upon a slow down threshold associated with the requesting client, an interval m connection request count for the requesting client, wherein the interval m connection request count is the total number of connection requests received during the interval m for the requesting client, and an interval m wait time. A throttling interval m+1 connection request count is set to zero and the server computer waits for the throttling interval m+1 wait time before accepting the request.
In a preferred embodiment, the throttling interval m+1 wait time is related to a difference between the interval m connection request count for the interval m and the slowdown threshold for that requesting client.
In another embodiment, in a client/server computer environment, an apparatus for restraining a connection request stream associated with a high volume connection request burst client is disclosed. The apparatus includes a connection request receiving unit for receiving a connection request at a beginning of a throttling interval m+1, where the throttling interval m+1 is subsequent to a throttling interval m. A memory unit coupled to the connection request receiving unit arranged to store data associated with a slow down threshold, an interval m connection request count for the requesting client, and an interval m wait time. The apparatus further includes a processor coupled to the memory arranged to calculate a throttling interval m+1 wait time based upon the slow down threshold associated with the requesting client, the interval in connection request count for the requesting client and further arranged to set a throttling interval m+1 connection request count to zero. A request throttler coupled to the processor is also included that is arranged to direct the server computer to wait the throttling interval m+1 wait time before accepting the request.
In yet another embodiment, a computer readable media including computer program code for restraining a connection request stream associated with a high volume connection request burst client is disclosed.